我需要从DataTable中选择行并按“Field1 / Field2”
对它们进行排序我试过这段代码：
package cct.mad.lab;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.DatePickerDialog;
import android.app.Dialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.text.format.DateFormat;
import android.util.Log;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
import java.sql.Time;
import java.util.Calendar;
public class SettingsActivity extends Activity {
private String DEBUG_TAG;
public final static String GAME_PREFERENCES = "GamePrefs";
public static final String GAME_PREFERENCES_NICKNAME = "Nickname"; // String
public final static String GAME_PREFERENCES_EMAIL = "Email"; // String
public final static String GAME_PREFERENCES_PASSWORD = "Password"; //String
public final static String GAME_PREFERENCES_DOB = "DOB"; // Long
public final static String GAME_PREFERENCES_GENDER = "Gender"; // Int
SharedPreferences mGameSettings;
static final int DATE_DIALOG_ID = 0;
static final int PASSWORD_DIALOG_ID = 1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.settings);
// Retrieve the shared preferences
mGameSettings = getSharedPreferences((String) GAME_PREFERENCES, Context.MODE_PRIVATE);
// Initialize the nickname entry
initNicknameEntry();
// Initialize the email entry
initEmailEntry();
// Initialize the Password chooser
initPasswordChooser();
// Initialize the Date picker
initDatePicker();
// Initialize the spinner
initGenderSpinner();
}
@Override
protected void onDestroy() {
Log.d(DEBUG_TAG, "SHARED PREFERENCES");
Log.d(DEBUG_TAG, "Nickname is: " + mGameSettings.getString((String) GAME_PREFERENCES_NICKNAME, "Not set"));
Log.d(DEBUG_TAG, "Email is: " + mGameSettings.getString((String) GAME_PREFERENCES_EMAIL, "Not set"));
Log.d(DEBUG_TAG, "Gender (M=1, F=2, U=0) is: " + mGameSettings.getInt((String) GAME_PREFERENCES_GENDER, 0));
// We are not saving the password yet
Log.d(DEBUG_TAG, "Password is: " + mGameSettings.getString((String) GAME_PREFERENCES_PASSWORD, "Not set"));
// We are not saving the date of birth yet
Log.d(DEBUG_TAG, "DOB is: "
+ DateFormat.format("MMMM dd, yyyy", mGameSettings.getLong((String) GAME_PREFERENCES_DOB, 0)));
super.onDestroy();
}
private void initNicknameEntry() {
// Save Nickname
final EditText nicknameText = (EditText) findViewById(R.id.EditText_Nickname);
if (mGameSettings.contains((String) GAME_PREFERENCES_NICKNAME)) {
nicknameText.setText(mGameSettings.getString((String) GAME_PREFERENCES_NICKNAME, ""));
}
nicknameText.setOnKeyListener(new View.OnKeyListener() {
public boolean onKey(View v, int keyCode, KeyEvent event) {
if ((event.getAction() == KeyEvent.ACTION_DOWN) && (keyCode == KeyEvent.KEYCODE_ENTER)) {
String strNickname = nicknameText.getText().toString();
Editor editor = mGameSettings.edit();
editor.putString((String) GAME_PREFERENCES_NICKNAME, strNickname);
editor.commit();
return true;
}
return false;
}
});
}
/**
* Initialize the email entry
*/
private void initEmailEntry() {
// Save Email
final EditText emailText = (EditText) findViewById(R.id.EditText_Email);
if (mGameSettings.contains((String) GAME_PREFERENCES_EMAIL)) {
emailText.setText(mGameSettings.getString((String) GAME_PREFERENCES_EMAIL, ""));
}
emailText.setOnKeyListener(new View.OnKeyListener() {
public boolean onKey(View v, int keyCode, KeyEvent event) {
if ((event.getAction() == KeyEvent.ACTION_DOWN) && (keyCode == KeyEvent.KEYCODE_ENTER)) {
Editor editor = mGameSettings.edit();
editor.putString((String) GAME_PREFERENCES_EMAIL, emailText.getText().toString());
editor.commit();
return true;
}
return false;
}
});
}
/**
* Initialize the Password chooser
*/
private void initPasswordChooser() {
// Set password info
TextView passwordInfo = (TextView) findViewById(R.id.TextView_Password_Info);
if (mGameSettings.contains((String) GAME_PREFERENCES_PASSWORD)) {
passwordInfo.setText(R.string.settings_pwd_set);
} else {
passwordInfo.setText(R.string.settings_pwd_not_set);
}
// Handle password setting dialog
Button setPassword = (Button) findViewById(R.id.Button_Password);
setPassword.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Toast.makeText(SettingsActivity.this, "TODO: Launch Password Dialog", Toast.LENGTH_LONG).show();
}
});
}
/**
* Initialize the Date picker
*/
private void initDatePicker() {
// Set password info
TextView dobInfo = (TextView) findViewById(R.id.TextView_DOB_Info);
if (mGameSettings.contains((String) GAME_PREFERENCES_DOB)) {
dobInfo.setText(DateFormat.format("MMMM dd, yyyy", mGameSettings.getLong((String) GAME_PREFERENCES_DOB, 0)));
} else {
dobInfo.setText(R.string.settings_dob_not_set);
}
// Handle date picking dialog
Button pickDate = (Button) findViewById(R.id.Button_DOB);
pickDate.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Toast.makeText(SettingsActivity.this, "TODO: Launch DatePickerDialog", Toast.LENGTH_LONG).show();
}
});
}
/**
* Initialize the spinner
*/
private void initGenderSpinner() {
// Populate Spinner control with genders
final Spinner spinner = (Spinner) findViewById(R.id.Spinner_Gender);
ArrayAdapter<?> adapter = ArrayAdapter.createFromResource(this, R.array.genders,
android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
if (mGameSettings.contains((String) GAME_PREFERENCES_GENDER)) {
spinner.setSelection(mGameSettings.getInt((String) GAME_PREFERENCES_GENDER, 0));
}
// Handle spinner selections
spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
public void onItemSelected(AdapterView<?> parent, View itemSelected, int selectedItemPosition,
long selectedId) {
Editor editor = mGameSettings.edit();
editor.putInt((String) GAME_PREFERENCES_GENDER, selectedItemPosition);
editor.commit();
}
public void onNothingSelected(AdapterView<?> parent) {
}
});
}
@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case DATE_DIALOG_ID:
final TextView dob = (TextView) findViewById(R.id.TextView_DOB_Info);
DatePickerDialog dateDialog = new DatePickerDialog(this, new DatePickerDialog.OnDateSetListener() {
public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {
Time dateOfBirth = new Time();
dateOfBirth.set(dayOfMonth, monthOfYear, year);
long dtDob = dateOfBirth.toMillis(true);
dob.setText(DateFormat.format("MMMM dd, yyyy", dtDob));
Editor editor = mGameSettings.edit();
editor.putLong(GAME_PREFERENCES_DOB, dtDob);
editor.commit();
}
}, 0, 0, 0);
return dateDialog;
case PASSWORD_DIALOG_ID:
LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
final View layout = inflater.inflate(R.layout.password_dialog, (ViewGroup) findViewById(R.id.root));
final EditText p1 = (EditText) layout.findViewById(R.id.EditText_Pwd1);
final EditText p2 = (EditText) layout.findViewById(R.id.EditText_Pwd2);
final TextView error = (TextView) layout.findViewById(R.id.TextView_PwdProblem);
p2.addTextChangedListener(new TextWatcher() {
@Override
public void afterTextChanged(Editable s) {
String strPass1 = p1.getText().toString();
String strPass2 = p2.getText().toString();
if (strPass1.equals(strPass2)) {
error.setText(R.string.settings_pwd_equal);
} else {
error.setText(R.string.settings_pwd_not_equal);
}
}
// ... other required overrides do nothing
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
}
});
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setView(layout);
// Now configure the AlertDialog
builder.setTitle(R.string.settings_button_pwd);
builder.setNegativeButton(android.R.string.cancel, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
// We forcefully dismiss and remove the Dialog, so it
// cannot be used again (no cached info)
SettingsActivity.this.removeDialog(PASSWORD_DIALOG_ID);
}
});
builder.setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
TextView passwordInfo = (TextView) findViewById(R.id.TextView_Password_Info);
String strPassword1 = p1.getText().toString();
String strPassword2 = p2.getText().toString();
if (strPassword1.equals(strPassword2)) {
Editor editor = mGameSettings.edit();
editor.putString(GAME_PREFERENCES_PASSWORD, strPassword1);
editor.commit();
passwordInfo.setText(R.string.settings_pwd_set);
} else {
Log.d(DEBUG_TAG, "Passwords do not match. Not saving. Keeping old password (if set).");
}
// We forcefully dismiss and remove the Dialog, so it
// cannot be used again
SettingsActivity.this.removeDialog(PASSWORD_DIALOG_ID);
}
});
// Create the AlertDialog and return it
AlertDialog passwordDialog = builder.create();
return passwordDialog;
}
return null;
}
@Override
protected void onPrepareDialog(int id, Dialog dialog) {
super.onPrepareDialog(id, dialog);
switch (id) {
case DATE_DIALOG_ID:
// Handle any DatePickerDialog initialization here
DatePickerDialog dateDialog = (DatePickerDialog) dialog;
int iDay, iMonth, iYear;
// Check for date of birth preference
if (mGameSettings.contains(GAME_PREFERENCES_DOB)) {
// Retrieve Birth date setting from preferences
long msBirthDate = mGameSettings.getLong(GAME_PREFERENCES_DOB, 0);
Time dateOfBirth = new Time();
dateOfBirth.set(msBirthDate);
iDay = dateOfBirth.monthDay;
iMonth = dateOfBirth.month;
iYear = dateOfBirth.year;
} else {
Calendar cal = Calendar.getInstance();
// Today's date fields
iDay = cal.get(Calendar.DAY_OF_MONTH);
iMonth = cal.get(Calendar.MONTH);
iYear = cal.get(Calendar.YEAR);
}
// Set the date in the DatePicker to the date of birth OR to the
// current date
dateDialog.updateDate(iYear, iMonth, iDay);
return;
case PASSWORD_DIALOG_ID:
// Handle any Password Dialog initialization here
// Since we don't want to show old password dialogs, just set new
// ones, we need not do anything here
// Because we are not "reusing" password dialogs once they have
// finished, but removing them from
// the Activity Dialog pool explicitly with removeDialog() and
// recreating them as needed.
return;
}
}
}
但是我收到错误，说“FirstNum / SecondNum”列不存在。
EDIT
到目前为止，我正在使用（作为一种解决方法）临时表，我正在添加一个字段，我存储比率，我正在使用该字段对表进行排序。
答案 0 :(得分：0)
我不认为select方法足够聪明，可以在现场进行计算。另一种解决方法是将计算列添加到数据表中，并将其用作排序列
答案 1 :(得分：0)
尝试将每列放在括号内
Using DT_Tmp As DataTable = DT.Select("", "[FirstNum] / [SecondNum] desc").CopyToDataTable
答案 2 :(得分：0)
根据您查看的链接，您需要先添加caluculated列。
csortnum= New DataColumn
With csortnum
.DataType = System.Type.GetType("System.Decimal")
.ColumnName = "sortcolumn"
.Expression = "FirstNum/SecondNum"
End With
DT.add(csortnum)
Using DT_Tmp As DataTable = DT.Select("", csortnum desc").CopyToDataTable